22 Feb Least cost nutrient adequate diets in NZ
We previously described the results of a modelling study that found the least cost nutrient adequate diet in the USA came in at US$1.98, and the equivalent least cost plant-only diet was $3.61. The authors of that study have now repeated their work with New Zealand data, reaching similar conclusions.
Linear programming was combined with supermarket food price data, food composition data and adult nutrient requirement data to find daily diets that met all nutrient requirements, optimised for cost.
Similarly to the original USA study, the least cost diet contained both plant- and animal-sourced foods. At NZ$3.23, the price difference to the plant-only diet (NZ$4.34) was reduced compared to the USA results.
In both the NZ and USA diets, milk was a large contributor to nutrient targets in the least cost diet. A soy beverage was the largest contributor to both mass and cost in the plant-only diets. Eggs, legumes, and cabbage were also important in both country settings. While fish was present in the USA least cost diet, this was replaced with green mussels in NZ.
The relative changes to the price of animal-sourced foods before they became priced out of the least cost diet differed between the two settings. Milk was removed when its price was 2.2x current NZ retail price (compared to 8x in the USA study); eggs under price increases of 1.8 times (11.5x in the USA study); and meat items under price increases of 1-2x (3-5.5x in the USA study). In contrast, the mussels remained in the least cost diet even if ten times more expensive than current prices.
This work reinforces the conclusions of the original paper: plant- and animal-sourced foods contribute to affordable, nutritious diets, and it can be more expensive to achieve adequate nutrient intakes if restricted to plant foods alone. However, the reduced resilience of most of the animal-sourced foods to price increases in the NZ setting is reflective of the differing relative retail prices of food in the two countries, which the authors state may be reflective of the influence of government subsidies in the USA.
Photo by Anastasiia Rusaeva on Unsplash